JP6394121B2 - Ester compound and lubricating oil and lubricating base oil containing the same - Google Patents

Description

The present invention relates to a hindered polyol ester compound which can be easily synthesized from various carboxylic acids and carboxylic acid esters under mild reaction conditions and has excellent viscosity index, heat resistance and color number, and lubricating oil and lubricating oil containing the same. Regarding base oil.

  Polyol ester and ester-based synthetic oils must have high functionality because they have a better balance of various physical properties such as viscosity characteristics, thermal stability, oxidation stability, lubricity, volatility, and low temperature characteristics than mineral oil. Is a synthetic oil widely used in the field of lubrication (Non-Patent Document 1). Among them, the hindered polyol ester does not have hydrogen at the β-position of the ester carbonyl group, so it does not undergo low-temperature low-temperature decomposition reaction via a pseudo-cyclic intermediate, and heat stability is a disadvantage of conventional synthetic synthetic oils. Excellent in heat resistance and oxidation stability, it has been widely used as a lubricant for heat-resistant applications.

  However, in various fields such as jet engine oil, automobile engine oil, air compressor oil, and flame retardant hydraulic oil, thermal stability and oxidation are further improved due to recent demands for higher performance, more severe use environment and longer life. Even in fields where lubricants with excellent stability are desired and low temperature characteristics are required, refrigerating machine oils with new characteristics are required due to environmental demands such as ozone layer destruction, and further excellent characteristics in various fields. Development of a polyol ester has been desired and studied.

  For example, in the field of heat resistance applications, esters of hindered carboxylic acids and hindered polyols have been studied for further improvement of heat resistance. Patent Document 1 illustrates a combination of a tertiary carboxylic acid and a polyhydric alcohol as an example of improved heat resistance and viscosity index. In particular, in order to increase oxidation stability, a combination of a hindered carboxylic acid and a hindered alcohol is desirable, but it is known that an esterification reaction of a combination of a hindered carboxylic acid and a hindered alcohol is difficult. (Patent Document 2). Therefore, a method of reacting an acid chloride with alcohol is generally used. Moreover, when acid chloride was not used, the reaction temperature had to be very high in the presence of a catalyst.

  On the other hand, in view of the viscosity index, a lubricating oil having a high viscosity index is generally desired (Patent Document 3). The viscosity index is a value calculated from the kinematic viscosities of 100 ° C. and 40 ° C. according to JIS K 2283, and the larger the viscosity index, the smaller the kinematic viscosity difference between 100 ° C. and 40 ° C. In general, it is known that when the viscosity increases, the frictional force increases and the mechanical efficiency decreases, whereas when the viscosity is too low, sufficient lubricity cannot be obtained and baking occurs. In other words, a high viscosity index means that it can be used as a lubricating oil in a wider temperature range, which is an important characteristic for lubricating oil, but a sufficiently high viscosity index can be achieved only with a lubricating base oil. In many cases, it is difficult to obtain, and a viscosity index improver is used in many applications. Thus, it is widely desired to develop a lubricating base oil having excellent viscosity characteristics.

  Usually, the improvement of the viscosity characteristics of the lubricating base oil is made by the ester part, ie the carboxylic acid and its derivatives. This is because hindered polyols that are widely used are almost limited to neopentyl glycol, trimethylolpropane, pentaerythritol, ditrimethylolpropane, and dipentaerythritol, and can be applied to these requirements. A polyol skeleton that provides new hindered polyol esters has been widely desired.

Japanese Patent No. 3894983 Special table 2009-501142 JP2012-219243

Jiro Hirano, Petrochemical, 1980, vol.29, no.9, p.627-635

As described above, there is no example in which an ester composed of dineopentyl glycol and an alkyl carboxylic acid was actually synthesized and identified, and physical properties for use as a lubricating oil were not examined in detail, and its performance was unknown.
Based on these backgrounds, the present invention provides hindered polyols and esters thereof that react with various hindered carboxylic acids and carboxylic acid esters under mild conditions and are excellent in viscosity index, oxidation stability, and color number. To do.

  As a result of intensive studies to achieve the above object, the present inventors have obtained an ester having excellent reactivity, viscosity index, oxidation stability and color number by using dineopentyl glycol. Has been found and has led to the present invention. That is, the present invention is as follows.

[1]
An ester compound represented by the general formula (1).
In the formula, each of R ¹ and R ² is independently selected from a linear saturated alkyl group having 1 to 20 carbon atoms, a branched saturated alkyl group, a linear unsaturated alkyl group and a branched unsaturated alkyl group, and R ³ , R Each ⁴ is independently selected from a linear alkyl group having 1 to 6 carbon atoms and a branched alkyl group.
[2]
The ester compound according to [1], wherein in formula (1), R ¹ and R ² are each independently a secondary or tertiary alkyl group having 4 to 15 carbon atoms.
[3]
The ester compound according to [1] or [2], wherein R ¹ and R ² are the same in formula (1) and are an alkyl group having 4 to 10 carbon atoms.
[4]
The ester compound according to any one of [1] to [3], wherein R ¹ and R ² are the same in formula (1) and are a secondary alkyl group or tertiary alkyl group having 4 to 10 carbon atoms.
[5]
[1] A lubricating oil comprising the ester compound according to any one of [4].
[6]
[1] A lubricating base oil comprising the ester compound according to any one of 1 to [4].
[7]
The manufacturing method of the ester compound which obtains the ester compound shown by General formula (1) by dehydration condensation reaction of the diol shown by General formula (2), and the carboxylic acid of General formula (3) and (4).
R ¹ COOH (3)
R ² COOH (4)
However, in the general formula (2), R ³ and R ⁴ are each independently selected from linear alkyl groups having 1 to 6 carbon atoms and branched alkyl groups, and in the general formulas (3) and (4) R ¹ and R ² are each independently selected from linear saturated alkyl groups having 1 to 20 carbon atoms, branched saturated alkyl groups, linear unsaturated alkyl groups, and branched unsaturated alkyl groups.
In the general formula (1), R ^{1 to} R ⁴ are as described above.
[8]
Catalysts in the dehydration condensation reaction are methanesulfonic acid, trifluoromethanesulfonic acid, p-toluenesulfonic acid, benzenesulfonic acid, dodecylbenzenesulfonic acid, sulfuric acid, solid acid catalyst containing sulfonic acid group, hydrochloric acid, phosphoric acid, titanium [9] The process for producing an ester compound according to [7], which is at least one selected from tetramethoxide, titanium tetraethoxide, titanium tetraisopropoxide, titanium tetrabutoxide, dioctyltin oxide and dibutyltin oxide.
Method for producing ester compound for obtaining ester compound represented by general formula (1) by transesterification reaction between diol represented by general formula (2) and carboxylic acid ester of general formula (5) and (6)
R ¹ COOR ⁵ (5)
R ² COOR ⁶ (6)
In the general formula (2), R ³ and R ⁴ are each independently selected from a linear alkyl group having 1 to 6 carbon atoms and a branched alkyl group, and in the general formulas (5) and (6), R ¹ , R ² is independently selected from a linear saturated alkyl group having 1 to 20 carbon atoms, a branched saturated alkyl group, a linear unsaturated alkyl group, and a branched unsaturated alkyl group, and R ⁵ and R ⁶ are each independently carbon. A saturated straight chain or saturated branched alkyl group having 1 to 4 is represented.
In the general formula (1), R ^{1 to} R ⁴ are as described above.
[10]
The catalyst in the transesterification reaction is at least selected from sulfuric acid, p-toluenesulfonic acid, titanate ester, zinc acetylacetone, dibutyltin oxide, sodium hydrogen carbonate, sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide and sodium methoxide The method for producing an ester compound according to [9], which is one.
[11]
In the formula (1), R ¹ and R ² are each independently a secondary or tertiary alkyl group having 4 to 15 carbon atoms [7] or [9]
The method for producing an ester compound according to [7] or [9], wherein in formula (1), R ¹ and R ² are equal and are a secondary alkyl group or tertiary alkyl group having 4 to 15 carbon atoms.
[13]
The method for producing an ester compound according to [7] or [9], wherein in formula (1), R ¹ and R ² are equal and are a secondary alkyl group or tertiary alkyl group having 4 to 10 carbon atoms.

  By using the polyol of the present invention, various polyol esters can be synthesized easily, and the obtained polyol ester has a small number of colors and is excellent in viscosity index and oxidation resistance, and can be applied in various fields. Therefore, the industrial significance of the present invention is considered to be great.

¹ H-NMR chart of dipivalic acid 4-oxa-2,2,6,6-tetramethylheptane-1,7-diyl obtained in Example 1 ¹ H-NMR chart of bis (2-ethylhexanoic acid) 4-oxa-2,2,6,6-tetramethylheptane-1,7-diyl obtained in Example 2 ¹ H-NMR chart of bis (3,5,5-trimethylhexanoic acid) 4-oxa-2,2,6,6-tetramethylheptane-1,7-diyl obtained in Example 3 ¹ H-NMR chart of 2,2-dimethylpropane-1,3-diyl dipivalate obtained in Comparative Example 1 ¹ H-NMR chart of bis (2-ethylhexanoic acid) 2,2-dimethylpropane-1,3-diyl obtained in Comparative Example 2 ¹ H-NMR chart of bis (3,5,5-trimethylhexanoic acid) 2,2-dimethylpropane-1,3-diyl obtained in Comparative Example 3

  Hereinafter, preferred embodiments of the present invention will be described in detail.

The ester compound of the present invention is represented by the general formula (1).
In the formula, each of R ¹ and R ² is independently selected from a linear saturated alkyl group having 1 to 20 carbon atoms, a branched saturated alkyl group, a linear unsaturated alkyl group, and a branched unsaturated alkyl group,
R ³ and R ⁴ are each independently selected from linear alkyl groups having 1 to 6 carbon atoms and branched alkyl groups.

In general formula (1), R ¹ and R ² are each independently preferably a secondary or tertiary alkyl group having 4 to 15 carbon atoms.
Moreover, it is more preferable in R < ¹ > and R < ² > in General formula (1) that it is equal and a C4-C10 alkyl group.
Further, in the general formula (1), it is more preferable that R ¹ and R ² are equal and are a secondary alkyl group or a tertiary alkyl group having 4 to 10 carbon atoms.

In the general formula (1), R ³ and R ⁴ are preferably each independently selected from a linear alkyl group having 1 to 3 carbon atoms and a branched alkyl group.

  The compound represented by the general formula (1) is synthesized by a dehydration condensation reaction of a diol and a carboxylic acid represented by the formula (2) or a transesterification reaction with a carboxylic acid ester.

In general formula (2), R ³ and R ⁴ are each independently selected from linear alkyl groups having 1 to 6 carbon atoms and branched alkyl groups.

The diol described in the general formula (2) can be obtained by hydrogenating and reducing the acetal of the general formula (3).
In the general formula (3), R ³ and R ⁴ are each independently selected from a linear alkyl group having 1 to 6 carbon atoms and a branched alkyl group.

The acetal described in the general formula (3) is obtained by acetalization of 2,2-dialkyl-3-hydroxypropionaldehyde and 2,2-dialkyl-1,3-propanediol as described in the formula (4). Can be obtained.
In general formula (4), R ³ and R ⁴ are each independently selected from linear alkyl groups having 1 to 6 carbon atoms and branched alkyl groups.

  The carboxylic acid that can be used in the dehydration condensation reaction may be any of saturated, unsaturated primary carboxylic acid, secondary carboxylic acid, and tertiary carboxylic acid. Examples of saturated linear primary carboxylic acid include caproic acid, enanthic acid, Caprylic acid, belargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, nonadecylic acid, arachidic acid, heicosyl, behenic acid, tricosylic acid and lignoceric acid Is given. More preferred are caproic acid, enanthic acid, caprylic acid, verargonic acid, capric acid, undecyl acid and lauric acid.

  The branched primary carboxylic acid and secondary carboxylic acid include structural isomers of these saturated linear primary carboxylic acids. Examples of branched primary alcohols include 3,5,5-trimethylhexanoic acid, 3-methylvaleric acid, 4-methylvaleric acid, 5-methylhexanoic acid, 4-methyloctanoic acid, 4-ethyloctanoic acid and 4-methylnonanoic acid and the like are raised. More preferred is 3,5,5-trimethylhexanoic acid. Examples of secondary alcohols include 2-methylpentanoic acid, 2-ethylpentanoic acid, 2-propylpentanoic acid, 2-methylhexanoic acid, 2-ethylhexanoic acid, 2-methylheptanoic acid, 2-ethylheptanoic acid, 2-methyloctanoic acid, 2-ethyloctanoic acid, 2,4-dimethyloctanoic acid, 2-hexyldecanoic acid, 2-heptylundecanoic acid, 2-methylhexadecanoic acid, 2-decyldodecanoic acid, 2-hexadecyloctadecanoic acid, iso Examples include myristic acid and isostearic acid. More preferably, 2-ethylpentanoic acid, 2-methylhexanoic acid, 2-ethylhexanoic acid, 2-methylheptanoic acid, 2-ethylheptanoic acid and 2-propylheptanoic acid are more preferable, and 2-ethylhexanoic acid is more preferable. 2-ethylheptanoic acid and 2-propylheptanoic acid.

  Examples of unsaturated primary carboxylic acids include α-linolenic acid, stearidonic acid, eicosapentaenoic acid, docosapentaenoic acid, linoleic acid, γ-linolenic acid, dihomoγ-linolenic acid, arachidonic acid, palmitoleic acid, vaccenic acid, Examples include pauric acid, oleic acid, elaidic acid, erucic acid, and nervonic acid.

Examples of the tertiary carboxylic acid include structural isomers of the above-mentioned saturated linear primary carboxylic acid, such as pivalic acid, 2,2-diisopropylpropionic acid, 2,2-dimethylbutyric acid, 2-methyl- 2-ethylbutyric acid, 2-ethyl-2,3,3-trimethylbutyric acid, 2,2-dimethylpentanoic acid, 2-methyl-2-ethylpentanoic acid, 2,2,3,3-tetramethylpentanoic acid, 2 , 2,3,4-tetramethylpentanoic acid, 2,2,4,4-tetramethylpentanoic acid, 2,2-dimethylhexanoic acid, 2,2-dimethylheptanoic acid, 2,2-dimethyloctanoic acid, 2,2-dimethylnonanoic acid, 2,2-dimethyldecanoic acid, 2,2-dimethylundecanoic acid, 2,2-dimethyldodecanoic acid, 2,2-dimethyltridecanoic acid, 2-methyl-2-ethyldodecanoic acid 2,2-dimethylpentadecanoic acid, 2-methyl-2-ethyltetradecanoic acid, 2,2-diethyltridecanoic acid, 2-methyl-2-ethyloctadecanoic acid, 2,2-diethylheptadecanoic acid and 2,2- Examples include diethyl nonadecanoic acid.

  Moreover, you may add 0.9 equivalent or less dicarboxylic acid as carboxylic acid. Examples of the dicarboxylic acid include adipic acid, pimelic acid, suberic acid, azelaic acid and sebacic acid.

  One kind of these carboxylic acids may be used, or two or more kinds may be mixed and used.

  The dehydration condensation reaction of dineopentyl glycol and carboxylic acid is usually performed at 100 to 250 ° C. The reaction time varies depending on the reaction scale and temperature, but it is performed in 1-20 hours. The pressure is normal pressure or reduced pressure. In the case of reduced pressure, the pressure is usually 0.1-80 kPa.

  An azeotropic solvent may or may not be used, and when used, a solvent having an appropriate boiling point is selected. For example, benzene, toluene, xylene, cumene, heptane, octane, decane, cyclohexane, decalin, chloroform, Examples thereof include 1,2-dichloroethane and chlorobenzene, preferably toluene and xylene. The amount of the solvent is 0.5 to 30 times by mass and preferably 1 to 10 times by mass with respect to the diol to be used. Moreover, you may use a solvent in mixture of 2 or more types.

Moreover, it is not necessary to use a catalyst, and when using a catalyst, 0.01-4 mass% is preferable. Usable as the catalyst are ordinary organic acids, inorganic acids, and Lewis acids, and these organic acids include alkane sulfonic acids and aryl sulfonic acids.
Examples of each catalyst include methanesulfonic acid and trifluoromethanesulfonic acid as alkanesulfonic acids, p-toluenesulfonic acid, benzenesulfonic acid and dodecylbenzenesulfonic acid as arylsulfonic acids, and inorganic acids as Sulfuric acid, hydrochloric acid and phosphoric acid, and examples of the Lewis acid include titanium tetramethoxide, titanium tetraethoxide, titanium tetraisopropoxide, titanium tetrabutoxide, dioctyltin oxide and dibutyltin oxide. Moreover, a catalyst can also be used in mixture of 2 or more types selected from the above.
In particular, in the case of a sulfonic acid catalyst having a PKa of 2 or less such as p-toluenesulfonic acid, methanesulfonic acid, and sulfuric acid, the reaction acceleration is remarkable.

  On the other hand, the molar ratio of dineopentyl glycol and carboxylic acid is 1.0: 2.0 to 4.0, preferably 1.0: 2.0 to 3.0. In particular, when p-toluenesulfonic acid or the like is used as a catalyst, the reaction can be performed with a reduced amount of carboxylic acid.

  The carboxylic acid ester that can be used in the transesterification reaction may be any of saturated primary carboxylic acid ester, unsaturated primary carboxylic acid ester, secondary carboxylic acid ester, and tertiary carboxylic acid ester. Examples of saturated primary carboxylic acid esters include methyl caproate, methyl enanthate, methyl caprylate, methyl verargonate, methyl caprate, methyl undecylate, methyl laurate, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid , Margaric acid, methyl stearate, methyl nonadecylate, methyl arachidate, methyl hehenosyl, methyl behenate, methyl tricosylate and methyl lignocerate. More preferred are methyl caproate, methyl enanthate, methyl caprylate, methyl verargonate, methyl caprate, methyl undecylate and methyl laurate. Examples of the saturated secondary and tertiary carboxylic acid esters include the structural isomers of the saturated primary carboxylic acid esters described above.

  Further, as unsaturated primary carboxylic acid ester, methyl α-linolenate, methyl stearidinate, methyl eicosapentanoate, methyl docosapentaenoate, methyl linoleate, methyl γ-linolenate, methyl dihomoγ-linolenate Methyl arachidonate, methyl palmitoleate, methyl bacsenate, methyl paurate, methyl oleate, methyl elaidate, methyl erucate and methyl nervonate.

  The transesterification reaction between dineopentyl glycol and a carboxylic acid ester is usually carried out at 100 to 250 ° C. while removing the produced alcohol from the reaction system. The reaction time varies depending on the scale and temperature of the reaction, but the reaction time is 1-20 hours. The pressure is normal pressure or reduced pressure. In the case of reduced pressure, the pressure is usually 0.1-80 kPa. Catalysts used for transesterification include acidic catalysts such as sulfuric acid and p-toluenesulfonic acid, Lewis acid catalysts such as titanate ester, zinc acetate, acetylacetone zinc and dibutyltin oxide, sodium bicarbonate, sodium carbonate, potassium carbonate, water Any basic catalyst such as sodium oxide, potassium hydroxide and sodium methoxide may be used. The amount of the catalyst used is preferably 0.1-4% by mass.

  By using the alcohol of the general formula (2), the dehydration condensation reaction with various carboxylic acids and the transesterification reaction with various carboxylic acid esters proceed more quickly and mildly than when using neopentyl glycol. In addition, a hindered polyol ester having a high yield and excellent viscosity index and color number can be obtained.

  The polyol ester of the present invention is usually used from weight-resistant additives, oiliness agents, antioxidants, detergent dispersants, antifoaming agents, rust inhibitors, demulsifiers, pour point depressants, viscosity index improvers, and the like. It is possible to mix at least one selected various additives as required.

  In addition, other lubricant base oils such as mineral oil, poly-alpha olefin, polybutene, alkylbenzene, animal and vegetable oils, organic acid esters, polyvinyl ether, polyphenyl ether, and alkylphenyl may be used as long as the performance is not deteriorated. It is also possible to mix and use at least one selected from ethers and the like.

  Using the polyol ester of the present invention as a base oil, grease, refrigerating machine oil, insulating oil, hydraulic hydraulic oil, gear operating system lubricating oil, cutting / grinding oil, transmission lubricating oil, wind power booster oil, internal combustion engine It can be used for applications such as lubricating oil for engines (engine oil), lubricating oil for power generation turbines, lubricating oil for compressors, lubricating oil for bearings.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not particularly limited to the following examples.

Analysis of the reaction was performed by gas chromatography. For gas chromatography, 6850 manufactured by Agilent Technologies was used. The column used was HP-1 manufactured by J & W. The column temperature was maintained at 100 ° C. for 5 minutes, then heated to 275 ° C. at 10 ° C./minute, and then maintained for 20 minutes. The injection temperature was 270 ° C., the detector was TCD, and the temperature was 290 ° C. Helium was used as the carrier gas.
The product was identified by ¹ H-NMR spectrum. The measured using JEOL Ltd. JNM-ECA500, solvent and CDCl _3, using tetramethylsilane as the internal standard.

Synthesis example 1
Synthesis of 2- (5,5-dimethyl-1,3-dioxan-2-yl) -2-methylpropan-1-ol

131.3 g of 2,2-dimethyl-3-hydroxy-propionaldehyde (hydroxypivalaldehyde, manufactured by Mitsubishi Gas Chemical Co., Inc., purity 99.8%) and 2,2-dimethyl-1,3-propanediol 136. 0 g, 705 g of benzene, and 3.0 g of granular Nafion (trade name “NR-50”, manufactured by Sigma-Aldrich) were placed in a 2-liter round bottom flask, and water produced under normal pressure was azeotroped with benzene. The mixture was extracted out of the system using a Dean-Stark trap and allowed to react until the distillation of water stopped. This was filtered and then recrystallized by concentrating and cooling to give 2- (5,5-dimethyl-1,3-dioxan-2-yl) -2-methylpropan-1-ol crystals. .

The catalyst used for hydrogenation of acetal was synthesized as follows.

Carrier preparation Zirconium oxide used as a carrier for the metal component was prepared by the following method.
A white precipitate was obtained by dropping 15.5 g of 28% aqueous ammonia with stirring into 505 g of an aqueous zirconium oxynitrate solution having a concentration of 25% by mass in terms of zirconium oxide (ZrO ₂ ). This was filtered, washed with ion-exchanged water, and then dried at 110 ° C. for 10 hours to obtain hydrous zirconium oxide. This is stored in a magnetic crucible, and subjected to a baking treatment at 400 ° C. for 3 hours in the air using an electric furnace, and then pulverized in an agate mortar and expressed as powdered zirconium oxide (hereinafter referred to as “carrier A”). .) The BET specific surface area (measured by a nitrogen adsorption method) of the carrier A was 102.7 m ² / g.

Catalyst preparation A catalyst containing palladium as a specific metal component was prepared by the following method.
0.66 mass% palladium chloride-0.44 mass% sodium chloride aqueous solution was added to 50 g of carrier A, and the metal component was adsorbed on the carrier. A formaldehyde-sodium hydroxide aqueous solution was added thereto to instantaneously reduce the adsorbed metal component. Thereafter, the catalyst was washed with ion-exchanged water and dried to prepare a 1.0% by mass palladium-supported zirconium oxide catalyst (hereinafter referred to as “catalyst A”).

Synthesis example 2
Synthesis of 4-oxa-2,2,6,6-tetramethylheptane-1,7-diol
In a 500 mL SUS reactor, 3.0 g of catalyst A, 60.0 g of 2- (5,5-dimethyl-1,3-dioxan-2-yl) -2-methylpropan-1-ol, and 1,4 -Dioxane 240g was put and the inside of a reactor was substituted with nitrogen gas. Thereafter, 8.5 MPa of hydrogen gas was charged into the reactor, and the reaction temperature was raised to 230 ° C., and the reaction was performed for 5 hours while maintaining the hydrogen pressure at 13 MPa. Then, after cooling and filtering the contents of the reactor to separate the catalyst, the desired product was obtained by recrystallization purification.

Example 1
Synthesis of synthesis of dipivalic acid 4-oxa-2,2,6,6-tetramethylheptane-1,7-diyl
4-Oxa-2,2,6,6-tetramethylheptane-1,7-diol (20.09 g, 106 mmol) and pivalic acid (24.78 g, 243 mmol, 2.3 eq) m-xylene (20.27 g) ) To the solution was added p-toluenesulfonic acid monohydrate (598.9 mg, 3.14 mmol, 3 mol%) at room temperature. Thereafter, the inside temperature was heated to 150 to 160 ° C. under nitrogen, and water was removed from the system by azeotropy with m-xylene. The mixture was heated for 10 hours, cooled, washed with a 5% aqueous potassium hydroxide solution, and then washed with water until the washing solution became neutral. The remaining carboxylic acid was distilled off under reduced pressure to obtain the desired product in 36.3 g, yield 96%. APHA was 33. In addition, the time course of the reaction was followed by GC.

¹ H-NMR
δ (ppm): 0.92 (s, 12H, 4XC H ₃ ), 1.21 (s, 18H, 2XC (C H ₃ ) ₃ ), 3.15 (s, 4H, 2XOC H ₂ ), 3. 86 (s, 4H, 2XC H ₂ OCO)

Example 2
Synthesis of bis (2-ethylhexanoic acid) 4-oxa-2,2,6,6-tetramethylheptane-1,7-diyl
4-Oxa-2,2,6,6-tetramethylheptane-1,7-diol (20.00 g, 105 mmol) and 2-ethylhexanoic acid (31.86 g, 219 mmol, 2.1 eq) m-xylene ( P-Toluenesulfonic acid monohydrate (604.8 mg, 3.18 mmol, 3 mol%) was added to the solution at room temperature. Thereafter, the inner temperature was heated to 160 to 170 ° C. under nitrogen, and water was removed from the system by azeotropy with m-xylene. The mixture was heated for 7.5 hours, cooled, washed with 5% potassium hydroxide, and then washed with water until the washing solution became neutral. The acid was distilled off under reduced pressure to obtain the desired product in 43.7 g and a yield of 94%. In addition, the time course of the reaction was followed by GC.

¹ H-NMR
δ (ppm): 0.86-0.91 (m, 12H, 2XC H ₃ CH ₂ + 2XC H ₃ CH ₂ ), 0.92 (s, 12H, 4XC H ₃ ), 1.20-1.35 ( _{m, 8H, 2XCH 3 C H} 2 C H 2), 1.42-1.66 (m, 8H, 2XCOCH (C H 2 CH 3) C H 2 CH 2), 2.23-2.31 (m , 2H, 2XOCOC H ), 3.14 (s, 4H, 2XOC H ₂ C), 3.87 (s, 4H, 2XC H ₂ OCO)

Example 3
Synthesis of bis (3,5,5-trimethylhexanoic acid) 4-oxa-2,2,6,6-tetramethylheptane-1,7-diyl
4-Oxa-2,2,6,6-tetramethylheptane-1,7-diol (20.0 g, 105 mmol) and 3,5,5-trimethylhexanoic acid (34.98 g, 221 mmol, 2.1 eq) P-Toluenesulfonic acid monohydrate (601.1 mg, 3.16 mmol, 3 mol%) was added to a toluene (20.0 g) solution at room temperature. Thereafter, the inside temperature was heated to 135 ° C. under nitrogen, and water was removed from the system by azeotropy with toluene. The mixture was heated for 7.5 hours, cooled, washed with 5% potassium hydroxide, and then washed with water until the washing solution became neutral. The acid was distilled off under reduced pressure to obtain the desired product in a yield of 47.29 g and a yield of 96%. APHA was 7.

¹ H-NMR
δ (ppm): 0.91 (s, 18H, 2XC (C H ₃ ) ₃ ), 0.92 (s, 12H, 4XC H ₃ ), 0.98 (d, 6H, J = 6.6 Hz, 2XC H ₃ CH _2), 1.12 1H of (dd, 2H, J = 6.2,14.1Hz , 2XC H 2 C (CH 3) 3), 1.25 (dd, 2H, J = 4.3 , 14.1 Hz, 2XC H ₂ C (CH ₃ ) ₃ 1H), 2.00-2.08 (m, 2H, 2XC H CH ₃ ), 2.13 (dd, 2H, J = 8.3) 14.2 Hz, 1H of 2XOCOC H ₂ ), 2.32 (dd, 2H, J = 5.7, 14.2 Hz, 1H of 2XOCOC H ₂ ), 3.14 (s, 4H, 2XOC H ₂ ), 3 .85 (d, 2H, J = 10.8Hz, 1H of _{2XC H 2 OCO), 3.89 (} d, 2H, J = 10. Hz, IH of _2XC H 2 OCO)

Example 4
Tracking of formation rate of dioctanoic acid 4-oxa-2,2,6,6-tetramethylheptane-1,7-diyl
To a mixed solution of 4-oxa-2,2,6,6-tetramethylheptane-1,7-diol (25.03 g, 131.4 mmol) and methyl octoate (52.05 g, 329 mmol, 2.5 eq), Orthotitanate tetraisopropoxide (383.7 mg, 1.35 mmol, 1 mol%) was added at room temperature. Thereafter, the mixture was heated to 140 to 145 ° C. under nitrogen, and the time course of the reaction was followed by GC.

Comparative Example 1
Synthesis of 2,2-dimethylpropane-1,3-diyl dipivalate
In the same conditions as in Example 1, using 2,2-dimethylpropane-1,3-diol instead of 4-oxa-2,2,6,6-tetramethylheptane-1,7-diol in Example 1. The reaction was carried out, and water was removed from the system by azeotropy with m-xylene. After cooling for 14 hours after heating, the diester was 59.6 Area% by GC analysis. After washing with 5% potassium hydroxide, it was washed with water until the washing solution became neutral. The acid was distilled off under reduced pressure, and the product was obtained by separating and purifying from monoester and the like by silica gel column chromatography.

¹ H-NMR
δ (ppm): 0.99 (s, 6H, 2XC H ₃ ), 1.21 (s, 18H, 2XC (C H ₃ ) ₃ ), 3.88 (s, 4H, 2XC H ₂ OCO)

Comparative Example 2
Synthesis of bis (2-ethylhexanoic acid) 2,2-dimethylpropane-1,3-diyl
In the same conditions as in Example 2, using 2,2-dimethylpropane-1,3-diol instead of 4-oxa-2,2,6,6-tetramethylheptane-1,7-diol in Example 2. The reaction was carried out, and water was removed from the system by azeotropy with m-xylene. After heating for 9 hours, the diester was 60.8 Area% by GC analysis. After that, the temperature was raised to 200 ° C., heated for 15 hours, cooled, washed with 5% potassium hydroxide, and water until the washing solution became neutral. Washed with. The acid was distilled off under reduced pressure, followed by separation and purification by silica gel column chromatography to obtain the desired product.

¹ H-NMR
δ (ppm): 0.86-0.91 (m, 12H, 2XC H ₃ CH ₂ + 2XC H ₃ CH ₂ ), 0.99 (s, 6H, 2XC H ₃ ), 1.20-1.35 ( _{m, 8H, 2XCH 3 C H} 2 C H 2), 1.42-1.66 (m, 8H, 2XCOCH (C H 2 CH 3) C H 2 CH 2), 2.25-2.32 (m , 2H, 2XOCO CH ), 3.894 (1H of s, 2H, 2XC H ₂ OCO), 3.896 (1H of s, 2H, 2XC H ₂ OCO)

Comparative Example 3
Synthesis of bis (3,5,5-trimethylhexanoic acid) 2,2-dimethylpropane-1,3-diyl
The same conditions as in Example 3, except that 2,2-dimethylpropane-1,3-diol was used instead of 4-oxa-2,2,6,6-tetramethylheptane-1,7-diol in Example 3. The water was removed from the system by azeotropy with toluene. The mixture was heated for 5 hours, cooled, washed with 5% potassium hydroxide, and then washed with water until the washing solution became neutral. The acid was distilled off under reduced pressure to obtain the desired product.

¹ H-NMR
δ (ppm): 0.91, (s, 18H, 2XC (C H ₃ ) ₃ ), 0.98 (s, 6H, 2XC H ₃ ), 0.98 (d, 6H, J = 6.6 Hz, 2XC H ₃ CH ₂ ), 1.13 (dd, 2H, J = 6.3, 14.0 Hz, 2XC H ₂ C (CH ₃ ) ₃ 1H), 1.24 (dd, 2H, J = 4. 0, 14.0 Hz, 1H of 2XC H ₂ C (CH ₃ ) ₃ ), 1.99-2.08 (m, 2H, 2XC H CH ₃ ), 2.14 (dd, 2H, J = 8.3 14.5 Hz, 2XOCOC H ₂ 1H), 2.33 (dd, 2H, J = 5.7, 14.5 Hz, 2XOCOC H ₂ 1H), 3.861 (d, 1H, J = 10.9 Hz) _{, C H 2 OCO), 3.866} (d, 1H, J = 10.9Hz, C H 2 OCO), 3.899 (d, 1 _{, J = 10.9Hz, C H 2} OCO), 3.905 (d, 1H, J = 10.9Hz, C H 2 OCO)

Comparative Example 4
Tracking of production rate of 2,2-dimethylpropane-1,3-diyl dioctanoate 2,2 instead of 4-oxa-2,2,6,6-tetramethylheptane-1,7-diol of Example 4 -Dimethylpropane-1,3-diol was used and the reaction was carried out under the same conditions as in Example 4. The time course of the reaction was followed by GC.

Example 5 and Comparative Example 5

The production rate of dipivalate ester in Example 1 and Comparative Example 1 was monitored by gas chromatography, and the GC area ratio of the diester after 10 hours was compared. The area ratio of diester is 100X (diester area) / (diester area + monoester area + diol area).
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Example 6 and Comparative Example 6
The production rate of bis (2-ethylhexanoic acid) ester of Example 2 and Comparative Example 2 was monitored by gas chromatography, and the GC area ratio of the diester after 6 hours was compared. The area ratio of diester is 100X (diester area) / (diester area + monoester area + diol area).
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As shown in Comparative Examples 5 and 6 in Tables 1 and 2, acid catalysts of 2,2-dimethylpropane-1,3-diol (neopentyl glycol) and tertiary / secondary carboxylic acid, which are used for general purposes, are used. In the dehydration condensation reaction used, the diester was 56% and 56% GC area ratio after 10 hours and 6 hours. With 2,6,6-tetramethylheptane-1,7-diol (dineopentyl glycol), the reaction completely proceeded under very mild conditions.

Example 7 and Comparative Example 7
The production rate of dioctanoic acid ester in the transesterification reaction of Example 4 and Comparative Example 4 was followed by gas chromatography, and the GC area ratio of the diester after 11.5 hours was compared. The area ratio of diester is 100X (diester area) / (diester area + monoester area + diol area).
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As shown in Table 3, 2,2-dimethylpropane-1,3-diol (neopentyl glycol), which is widely used in the transesterification reaction using orthotitanate tetraisopropoxide, which is often used for ester synthesis As shown in Example 7, surprisingly, the reaction of carboxylic acid ester with carboxylic acid ester produced no diester form as in Comparative Example 7. With tetramethylheptane-1,7-diol (dineopentyl glycol), the reaction proceeded under very mild conditions.
Thus, compared to neopentyl glycol, dineopentyl glycol undergoes an esterification reaction under extremely mild conditions in acid-catalyzed dehydration condensation reaction and Lewis acid-catalyzed transesterification reaction, making it easy to form hindered esters that are difficult to synthesize. It was found that can be synthesized.

The resulting ester was measured for kinematic viscosity and the viscosity index was determined.
Kinematic viscosity: Kinematic viscosity was determined according to JIS K2283 using an Ubbelohde viscometer.
Viscosity index: determined from kinematic viscosity at 40 ° C. and 100 ° C. according to JIS K2283.

Example 8 and Comparative Example 8
The kinematic viscosity of the 2-ethylhexanoic acid diester obtained in Example 2 and Comparative Example 2 was measured to determine the viscosity index.

  In the ester with 2-ethylhexanoic acid which is a secondary carboxylic acid, as shown in Table 4, the viscosity index was improved with dineopentyl glycol as compared with neopentyl glycol.

Example 9 and Comparative Example 9
The kinematic viscosity of the 3,3,5-trimethylhexanoic acid diester obtained in Example 3 and Comparative Example 3 was measured to determine the viscosity index.

  In esters with 3,3,5-trimethylhexanoic acid, which is a primary carboxylic acid, as shown in Table 5, the viscosity index was improved with dineopentyl glycol as compared with neopentyl glycol.

Example 10 and Comparative Example 10
The kinematic viscosity of the diester of pivalic acid obtained in Example 1 was measured to determine the viscosity index. The kinematic viscosity of the diester of pivalic acid obtained in Comparative Example 1 was measured.

The dipivalate ester of neopentyl glycol had a kinematic viscosity at 100 ° C. of 2 cSt or less, and the viscosity index could not be determined.
Therefore, another evaluation was performed. JISK2283 has a relational equation between kinematic viscosity and temperature.

loglogZ = A-Blog (273.15 + t)

It is described that the following formula holds.
A: Numerical value representing intercept, B: Numerical value representing gradient, t: Temperature, Z: Kinematic viscosity + correction value

The smaller the constant B representing the gradient, the smaller the change in viscosity with respect to temperature, and the constant B was determined and compared. As a result, as shown in Table 6, the constant B was smaller in Example 10 than in Comparative Example 10, and it was found that excellent viscosity characteristics were exhibited.

  Thus, in various carboxylic acid esters of dineopentyl glycol, the viscosity index was larger than that of general-purpose neopentyl glycol, and improvement was observed.

  The ester compounds synthesized from the polyol of the present invention and various carboxylic acids / carboxylic esters are greases, refrigerator oils, insulating oils, hydraulic hydraulic oils, gear operating system lubricants, cutting / grinding oils, and transmission lubricants. It can be used in a wide range of applications such as oil, speed increaser oil for wind power generation, lubricating oil for internal combustion engines (engine oil), lubricating oil for power generation turbines, lubricating oil for compressors and lubricating oil for bearings.

Claims (9)

An ester compound represented by the general formula (1).
In the formula, R ¹ and R ² are the same group, and are a secondary alkyl group having 5 to 10 carbon atoms,
R ³ and R ⁴ are each independently selected from linear alkyl groups having 1 to 6 carbon atoms and branched alkyl groups. R ¹ , R ² The ester compound according to claim 1, which is derived from 2-ethylhexanoic acid. A lubricating oil comprising the ester compound according to claim 1 or 2 . A lubricating base oil comprising the ester compound according to claim 1 . The manufacturing method of the ester compound which obtains the ester compound shown by General formula (1) by dehydration condensation reaction of the diol shown by General formula (2), and the carboxylic acid of General formula (3) and / or (4).
R ¹ COOH (3)
R ² COOH (4)
However, in the general formula (2), R ³ and R ⁴ are each independently selected from linear alkyl groups having 1 to 6 carbon atoms and branched alkyl groups, and in the general formulas (3) and (4) R ^1, R ² are the same group, and Ru 2 alkyl groups der 5 to 10 carbon atoms.
In the formula, R ¹ and R ² are the same group, and are a secondary alkyl group having 5 to 10 carbon atoms,
R ³ and R ⁴ are each independently selected from linear alkyl groups having 1 to 6 carbon atoms and branched alkyl groups. Catalysts in the dehydration condensation reaction are methanesulfonic acid, trifluoromethanesulfonic acid, p-toluenesulfonic acid, benzenesulfonic acid, dodecylbenzenesulfonic acid, sulfuric acid, solid acid catalyst containing sulfonic acid group, hydrochloric acid, phosphoric acid, titanium 6. The method for producing an ester compound according to claim 5, wherein the ester compound is at least one selected from tetramethoxide, titanium tetraethoxide, titanium tetraisopropoxide, titanium tetrabutoxide, dioctyltin oxide and dibutyltin oxide . Method for producing ester compound for obtaining ester compound represented by general formula (1) by transesterification of diol represented by general formula (2) and carboxylic acid ester of general formula (5) and / or (6) .
R ¹ COOR ⁵ (5)
R ² COOR ⁶ (6)
In the general formula (2), R ³ and R ⁴ are each independently selected from a linear alkyl group having 1 to 6 carbon atoms and a branched alkyl group, and in the general formulas (5) and (6), R ¹ , R ² is the same group and is a secondary alkyl group having 5 to 10 carbon atoms, and R ⁵ and R ⁶ each independently represents a saturated straight chain or saturated branched alkyl group having 1 to 4 carbon atoms.
In the formula, R ¹ and R ² are the same group, and are a secondary alkyl group having 5 to 10 carbon atoms,
R ³ and R ⁴ are each independently selected from linear alkyl groups having 1 to 6 carbon atoms and branched alkyl groups. The catalyst in the transesterification reaction is at least selected from sulfuric acid, p-toluenesulfonic acid, titanate ester, zinc acetylacetone, dibutyltin oxide, sodium hydrogen carbonate, sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide and sodium methoxide The method for producing an ester compound according to claim 7 , wherein the number is one. R ¹ , R ² Is a method for producing an ester compound according to any one of claims 5 to 8, derived from 2-ethylhexanoic acid.